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Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Medical Editor:

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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The cause of CFS is unknown, but the condition may be related to infection with effects on the immune system. Several viruses have been studied as possible causes of CFS, but no cause-and-effect relationship has been discovered. Some evidence indicates that the bacterium Chlamydia pneumoniae (which causes pneumonia and other illnesses) may be a cause of CFS in some cases. People with chronic fatigue syndrome related to C. pneumoniae are most likely to respond to antibiotics that kill C. pneumoniae, and their CFS symptoms may improve with antibiotic medications such as doxycycline. However, this association is still being debated. Various unrelated infections appear to lead to long-term fatigue in some people. If the fatigue is accompanied by problems with short-term memory or concentration, CFS is possible.

• One of the associated infections is the Epstein-Barr virus, or EBV. EBV causes mononucleosis, also called "mono" or the "kissing disease." Although associated in some cases, EBV does not cause CFS, and CFS is not the same thing as long-term EBV infection or long-term mononucleosis.



• Other unrelated infectious diseases that appear to lead to fatigue include pneumonia, diarrhea, and bronchitis.



• Candida albicans infections (or yeast infections) do not cause CFS.

• adrenal insufficiency,



• malignancy,



• AIDS,



• liver disease,



• kidney disease,



• psychosomatic illness,



• Lyme disease,



• fibromyalgia,



• hepatitis C, and



• thyroid disease.

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